Decaffeinate event-kit

[wbinnssmith]

This:

• Runs eventkit through decaffeinate
• Manually cleans up unnecessary code from decaffeinate
• Removes coffeelint and coffee-script build steps
• Removed lib from .gitignore as lib is now the source files (no build steps!)
• Converts the Gruntfile to js
• Formats the js to roughly comply with other Atom packages

Notes:

• event-kit now requires a modern version of Node/Electron. Let me know if we need this compatible with older environments (e.g. browsers) and I can add a build step through babel.
• In Emitter, Disposable, and CompositeDisposable, I removed declaring disposed = false from the respective prototype to the constructors for each instance. This feels like more idiomatic js, but if this was placed on the prototype as an optimization, please let me know.
• In a few places, I cleaned things up to be more readable and idiomatic js rather than preserving a strict interpretation of the CoffeeScript behavior. e.g.

    const handlers =
      this.handlersByEventName && this.handlersByEventName[eventName]

...instead of a ternary handling the null case, this short circuits on the falsey case, as this.handlersByEventName should only ever be a nullable object. Happy to tighten this up if desired.

Test Plan: npm test and linked this package with Atom and Nuclide and smoke tested superficial features

[maxbrunsfeld]

🔥 ?

[wbinnssmith]

👍